This application claims the priority of Korean Patent Application No. 10-2004-0107224, filed on Dec. 16, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a micro stage, and more particularly, to a micro stage employed in a micro-column electron beam apparatus, which is mounted in an ultra high vacuum chamber and is capable of stably positioning an electron emission tip on an electron lens module without coupling effects.
2. Description of the Related Art
Efforts have been made world wide to miniaturize micro stages employed in micro-column electron beam apparatuses. The micro stages are applied to scanning tunneling microscopes, which align an emission tip, which is an electron beam source essential to all electron beam apparatuses, along an optical axis and operate the emission tip in a field emission mode.
FIGS. 1 and 2 are respectively a perspective view and an exploded perspective view of a conventional micro stage employing piezoelectric elements that are used to move an electron beam source tip module along X, Y, and Z axes.
A stage module 100 employed in a conventional micro-column electron beam apparatus functions as a three-axis positioner. The stage module 100 includes four stainless steel stages, that is, a base frame 101, an Y-axis sliding state 110, an X-axis sliding state 120, and a Z-axis sliding state 130.
This structure is instrumentally complex and physically requires various additional functions, each causing operational problems. Also, slow motion of piezoelectric (PZT) actuators 102 results in friction between the stages, and fast motion of the PZT actuators 102 causes the stages to slip from their desired positions due to their inertia.
In general, each of the PZT actuators 102 moves the stages by approximately 10 μm when 100 V is applied to the PZT actuators 102. To make the moving stages slide, both a rigid bearing and smooth sliding surface should be used. Steel and sapphire, which have a smooth sliding surface, may be used for the smooth sliding bearing. A guide bearing which has V-grooves 112 of several millimeters may be disposed in the moving base frame 101 at an angle of 90 degrees. Ball sliding bearings may be placed in the V-grooves 112 to act as guiding bearings.
In the conventional stage module 100, a large force is applied to contact surfaces so that the V-grooves 112 over a half rod 114 can slide to press the contact surfaces and reduce friction generated at the contact surfaces. However, this structure has disadvantages of poor alignment of the V-grooves 112 when the V-grooves 112 are mechanically processed. In addition, as the contact surfaces increase, a pressure higher than the ball bearings is produced.
A leaf spring 113 is used for pressing the moving stages, not a coil spring. The leaf spring 113 is fairly stiff in a direction perpendicular to a direction in which it is flexible.